1. Field of the Invention
This invention relates to an apparatus, method and system for reducing the noise generated by gas turbine engines, particularly aircraft gas turbine engines. More particularly, this invention relates to an apparatus in which a separate gas stream such as air is introduced at one or more engine nozzle portions to disrupt the noise-generating gas streams ordinarily generated by the engine exhaust. The method and system of this invention use such an apparatus to reduce gas turbine engine noise, particularly during high noise generating periods such as aircraft takeoff.
2. Background Information
The desirability of reducing noise generated by gas turbine engines is well known to those skilled in the art. More particularly, it is well known that gas turbine engines used in aircraft generate undesirable noise levels, particularly during the takeoff period of the aircraft. Extensive testing on using tabs and chevrons in aircraft gas turbine engine exhaust mixers have shown promise in reducing engine exhaust noise during takeoff. It is believed that such tabs and chevrons break up the large scale, low frequency exhaust flow into smaller, high frequency components. These high frequency components are believed to dissipate quickly in the atmosphere without reaching the ground. However, the performance losses associated with the use of such tabs and chevrons becomes prohibitive for long range aircraft where cruise performance is the driving design parameter. Accordingly, it is desirable to employ a method, apparatus and system for reducing noise in such engines which avoids such detrimental cruise performance losses.
Accordingly, it is one object of this invention to provide an apparatus to reduce gas turbine engine noise, particularly during high noise generating periods such as aircraft takeoff, while minimizing aircraft cruise performance losses. In the apparatus of this invention at least one separate gas stream is introduced proximate to or at one or more engine nozzle portions to disrupt the noise-generating gas streams ordinarily generated by the engine exhaust. The method and system of this invention use such an apparatus to reduce gas turbine engine noise, particularly during high noise generating periods such as aircraft takeoff, yet avoid or minimize detrimental cruise performance losses. Other objects, features and advantages of the apparatus, method and system of this invention will be apparent from the detailed description herein.